Sigma 12-24mm Part 2

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Dylanlewis2000

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Well, just to give you an insight in to the Sigma, I originally bought a Sigma 12-24 last Friday on a random spending spree. The Sigma was bought and taken home. Upon testing the lens was very soft of the left hand side. The lens was taken back to Jessops where they ordered me a new one from another store. The store they phoned said that they had two in stock and one was brand new in a box and had not been opened. The new one arrived today in Nikon box, but thankfully it was a Canon fit, however the lens did have specs of dust on the front element suggesting that it was taken off display.

The lens itself felt stiff which is nice and on first impressions everything looked ok. I have taken the lens out and taken some photos with it, but something is telling me it's not quite right. 100% crops are not as sharp as they could be. Compared to my other lens this seems soft, even my 17-85 seems to be a bit sharper. Is this normal?

This shot below was shot handheld and square on the wall

1.jpg


Is it me or does the top look higher on the right than it does on the left? Is the lens supposed to do this or is this a fault?
This image of a tree was shot in good light and looks to be sharp zoomed out.

2.jpg


A 100% crop from the centre reveals that it just doesn't look sharp enough for an EX lens.

C2.jpg


Am i expecting too much from a Wide Angle lens? I have tried a Tamron 10-24mm and that was a pile of pap... well their copy was anyway and the canon 10-22 was grossly overpriced in Jessops. I just feel that this is the second sigma 12-24 i have had and it just doesn't seem right.
 
no, thats not good enough. Let me find you a crop from mine...

Sorry, another dud there!
 
You took these images at the "wide" end of the lens' aperture - f5.6 and f4.5 where they aren't going to be at their sharpest. Remember these were also handheld and on a 400D - not a bad camera at all, but reasonably entry-level.

Your best bet for testing would be to use a sheet of newspaper taped to the wall, with the camera on a tripod and use the timer or a remote release to trigger the shutter in a well lit room.

Remember that this isn't Canon 'L' glass - it's Sigma, and although they make good lenses they are cheaper than Canon for a reason!
 
Humm true MarkP, but thing is its their EX range, im not always going to have a tripod around with me, and shooting with my other EX lenes wide open they are still sharp.
 
Dylanlewis2000 said:
Humm true MarkP, but thing is its their EX range, im not always going to have a tripod around with me, and shooting with my other EX lenes wide open they are still sharp.
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I doubt its a lack of tripod issue - you are 4x safe handholding vs focal length.

It could well be shake, but a wide angle lens is nice and easy to handhold.

For safely try again on a tripod. But having had numerous duds myself I am always suspicious of these lenses. But a good one is very good.
 
I think what Mark means is that for a scientific test, you MUST remove all posibilities of you introducing any error.
If you use a tripod and timer, then that is the best you can expect from the lens. It will not be improved being used hand-held.
If you are hand-held, then using a tripod /might/ improve the picture.
 
That's fair enough. My 24-70 is perfect. My 10-20 is a bit soft down one side I think, but I need to do some proper tests. Some photos look fine, others less-so. I think it's the luck of the draw with Sigma.
 
Go with a tripod and remote release for testing.

Your 'brick wall' test shot doesn't appear to be level or square on to me. :)
 
If you are not completely satisfied with the lens then send it back IMO. How about looking at the Sigma 10-20 or better still (;)) the Tokina 12-24 (with the added benefit of Tokina having good QC).
 
i didnt like the idea of 10mm as there is going to be more distortion.
 
The the Tokina 12-24 is the one for you then. :)
 
Jessops dont do the Tokina do they? What does the Tokina offer?
 
Sigma.... I went through 3 copies of my 10-20mm before I got a good'un
 
Dylanlewis2000 said:
Jessops dont do the Tokina do they? What does the Tokina offer?
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The 12-24mm and the 11-16mm UWA lenses from Tokina are very highly regarded. I owned the 12-24mm when I had a cropped-sensor camera; excellent optics and a very rugged build quality.
 
I don't see how you can conclude anything much from those test pictures. I'm not saying you have a perfect lens there, just that you cannot really say it's duff from what you've shown.

You are not square to the wall, not by a long way. And you don't want to be shooting a flat target close up anyway, as all wide angles suffer from a bit of field curvature which is irrelevant in practise but could easily throw such a test. Shooting a newspaper will be even worse.

The crop image is not sharp enough in what respect? Compared to what? How was the image processed? Unless you have an exact A vs B comparison with a lens of known good quality, shots like this in isolation are very hard to assess.

Shoot a distant target, which will minimise potential focusing errors and eliminate field curvature issues. A road sign or car number plate is good, and take five pictures with the target in the centre and all four corners of the frame, with the lens at 20mm. Do exactly the same with your Canon 17-85.

Now take a peek. The four corner images should all look the same, even if they're not very sharp, which they won't be (it's a tough test). If they are the same, you have a 'good copy' and if one or more corners is markedly less sharp than the others, you do not.

To see if the lens is sharp enough for you, compare the pictures with the same set from your 17-85.
 
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